Method of making a fuel gas



g- 21, 1956 E. s. PETTYJCHN ET AL 2,759,806

METHOD OF MAKING A FUEL GAS Filed Feb. 16, 1953 NATURAL STEAM GAS LIQUIDV. V FURNACE TUBE- NICKEL CATALYST co H I FUEL GAS a VAPOR II Ir IRONCATALYST co H V I CONDENSER --SCRUBBER FUEL TARS C a GAS f wezyz'bzzf13727202? JfPezZg/ofzzz Fizzy ("y ZlzWdQZZ United States Patent2,759,806 Patented Aug. 21, 1956 amounts ranging from 20 to 60 or mores. c. f./ gallon of starting material.

When natural gas liquids are cracked under the conditions describedhereinabove, carbon is formed in such METHOD OF MAKING AFUEL GAS 5 smallamounts (less than 2% of the starting material) that the cracking mayconveniently be carried out con- Elmore Petty-ohm Evimston and X Lindentinuously (for periods such as 24 hours) in a suitable $23 33 i g 'fi gagg gl ig fifi f g furnace tube. Further, the yield of fuel gas inincreased g more than 20% over that obtained in conventional crack-Application February 16', 195 Serial N 337,078 ing methods, and the fuelgas is completely or absolutely 5 Claims. (CL 48 197) interchangeablewith natural gas in gas burners adjusted for natural gas. For instance,in the case of propane, 97% of the starting material is gasified to forma fuel gas of 1031 B. t. u./s. c. f. diluent free heating value and aspecific gravity of 0.55 (:air=1.000). In the case of This inventionrelates to a thermal cracking method 12 1b. R, V, P. natural gasoline,77% of the starting for converting natural gas liquids and petroleumoils into i l i ifi d t form a f l gas f 971 fuel gases. B. t. u./s. c.f. diluent free heating value and a specific An important Object of thepresent invention is to gravity of 0.53 (air=1.000). Both of these twofuel Provide a method of the nature indicated capable 0f gases areabsolutely interchangeable with natural gas. converting or at least amuch greater Portion than The character of the liquid by-products (tarsand light has heretofore been possible, of the cracked natural gas 11 ii ll h same as that f the liquid liquids Petroleum Oils into fuel gasabsolutely intefproducts of conventional thermal cracking of the sameChangeable with natural gas when burned in burner starting materials,although the amounts of such liquid adjusted for natural gas.by-products formed are greatly reduced, as compared Other and furtherobjects and features of the present ith nv tio l processes inventionWill become pp from the following The procedural steps of carrying outthe methods of SCIJ'PtiOH and pp claims as illustrated y the {116- thepresent invention need not differ from conventional chmpahyihg fiOWsheetShowing, y y of an p cracking methods, apart from the steps required tomaina process according to the present invention. tain the abovedisclosed conditions. Thus, the starting The starting materials employedin the method of material and the hydrogen are passed through a heatedthis invention include the natural gas liquids such as prostainlesssteel tube. The resulting oil gas is passed pane, butane and naturalgasoline. Distillate petroleum through conventional cooling andcondensing equipment oils may also be used. to remove and recover anytar and light oils formed.

According to the present invention, the starting mate- Any remaining tarfog may next be removed with an elecrial (in vapor form) is thermallycracked (in absence of trostatic precipitator. catalyst) underconditions disclosed as follows: The tem- By way of illustrativeexample, the conditions and perature ranges from 1400 to 1600 F., andpreferably results of a number of cracking runs are tabulated hereiskept at from 1450 to 1550" F. The contact time inbelow. These runs werecarried out using no hydro ranges from 2 to 10 seconds, and preferablyis kept at gen, as well as with various amounts of hydrogen, to from 4to 5 seconds. The pressure ranges from 2.5 to afford a comparison. RunsNos. 225, 384, 385, 387 and 7 or 8 or more atmospheres absolute, andpreferably is 388 were carried out with 12 lb. Reid vapor pressuremaintained at from 3 to 5 atmospheres absolute. The natural gasoline.Runs Nos. 243 and 389 were carried cracking is carried out in thepresence of hydrogen in out with propane.

TABLE I Operating and burner test data for pressure hydrogasification ofnatural gas liquids Run No 225 384 385 387 388 243 389 OperatingConditions: 20. 49 47. 57. 94 0 40. 83

Carrier Gas H2, S. O. FJGal. Hydrocarbon 0 27. 17 '5. 12 2. 96 5. 103.05 5. 01 Total Pressure, Atm 3. 11 3. 05 '60. 9 29.1 60. 5 30. 3 59. 2Gauge Pressure, P. S. l 31. 4 30. 4 1, 470 1,480 l, 480 l, 500 1, 470Cracking Temp., "F 1, 500 1, 420 92 4. 95 5.01 4. 23 4. 42 ResidenceTime, Sees 4. 91 4. 72 Operating results:

B. t. u. Recovery, M B. t. u./Gal- 74. 70 86. 48 82. 70 89.68 87. 32 76.18 S7. 47 Oil Gas Yield) S. O. FJGal. 70. 2 71. 22 67. 69 t 75. 36 81.86 73.82 69. 77 H2 Absorbed, S. C. FJGal. 13.83 6. 39 5. 76 18. 83 30.8013. 36 13.13 Tar yield, Wt. percent. Z 39. 6 22.6 27. 6 19. 8 20. 3 222.2 0 Light 011 Yield, Wt percent 1, 549 1 0. 420 1.691 0.417 0.599Carbon Yield, Wt. =percent 2. 47 1. 0 1. 1 1. ;2 1. 2 0. 1. 9 MaterialBalance, percent 99. 7 98. 7 97.0 99. 2 98. 2 102.9 99. 1

Gas Properties t Gas Composition, Inert-Free, Vol. prcenti H: 20.1 28.457.4 43. 5 5. 2 12. 0 0. 1 1. 4 0.1 0. 1 0. 2 14.6 4. 7 2. 7 2. 7 16.011.8 1. 2 0.7 0.9 0. 4 0. 9 1.6 0.1 0.2 02 0.1 0.2 0.1 0.2 PentenesTABLE I.Continued passed over an iron catalyst for the Water gas shiftreaction:

Next, to raise the hydrogen concentration, the carbon dioxide-hydrogengas mixture is scrubbed to remove the 70 carbon dioxide, by any suitableconventional method.

Reference is made to the accompanying flowsheet for the combinedcracking--hydrogen generating steps which may be carried outcontinuously as one form of the present invention. This flowsheet isbelieved self-explanatory. Each of the above indicated reactions beingknown per se, a person skilled in the art will know how to carry For Themethod of this invention, when applied to natural gas liquids as acontinuous furnace tube operation, may include a hydrogen generatingstep in which a part of 65 CnI Im+I1H20 nCO+ (n+m/2)H2 The product gasis then cooled to 700 to 1000 F. by water injection and the resultantsteam-gas mixture the feed stream is utilized as a source of hydrogen.

this purpose, a part of the hydrocarbon feed stream is passed over anickel catalyst with an amount of steam and at a temperature sufiicientto bring nearly to completion the reaction:

(with such added steam as may be required to force the 75 next followingreaction to go nearly to completion) is out the combined process in thelight of the disclosure given herein.

In general, about to of the feed stream may be converted into hydrogen,as by the method disclosed above. About 10% will usually besatisfactory. The amounts of hydrogen thus obtainable are exemplified asfollows: One gallon of propane is capable of yielding 40 s. c. f.hydrogen, and one gallon of 12 lb. R. V. P. natural gasoline is capableof yielding 52 s. c. f. hydrogen.

Thus, according to the present invention, natural gas liquids andpetroleum oils may be converted into fuel gases with a fuel gas yieldhigher than has heretofore been possible and with 20% less of liquidbyproducts, as compared with conventional oil gas processes. Further,the fuel gas obtained is absolutely interchangeable with natural gas.Reference -is made to our copending application Serial Number 270,955(filed February 11, 1952 and entitled Fuel Gas Interchangeable withNatural Gas and Method of Preparing the Same), now Patent No. 2,707,675,for a discussion of the interchangeability of fuel gases with eachother.

The above noted features of the method of the present invention are ofnotable value. The demand for a fuel gas absolutely interchangeable withnatural gas arises from the occurrence of a few days of peak gasrequirement in the areas supplied with natural gas for domestic and/orindustrial heating. On such days, the gas requirement rises above thedelivery capacity of the pipe lines and must be met from other sources.The method of the present invention can supply large volumes of fuel gasinterchangeable with natural gas without at the same time producinglarge amounts of liquid by-products, and the apparatus required topractice our methods can be relatively simple and inexpensive, which isimportant in view of the few days to which operation is confined.

Reference is made to our copending applications Serial Numbers 270,955(filed February 11, 1952, and entitled Method of Making a Fuel GasInterchangeable with Natural Gas, now Patent No. 2,707,675), 275,952(filed March 11, 1952, and entitled Method of Making Oil GasInterchangeable with Natural Gas), 287,122 (filed May 10, 1952 andentitled Method of Making Oil Gas Interchangeable with Natural Gas, nowPatent No. 2,721,123) and 311,256 (filed September 24, 1952 and entitledThermal Method of Making Oil Gas, now Patent No. 2,721,- 122). Theseapplications disclose cracking methods for making oil gas in which thefuel gas yield can be increased by adding hydrogen in amounts of from 20to 60 s. c. f./ gallon of liquid feed when the feed is cracked.

Many details may be varied without departing from the principles of thisinvention. Therefore, we do not intend to limit the scope of this patentotherwise than necessitated by the scope of the appended claims.

We claim:

1. A thermal cracking method (in absence of catalyst) of converting ahydrocarbon taken from the group consisting of propane, butane andnatural gasoline into a fuel gas interchangeable with natural gas whichcomprises passing said hydrocarbon in vapor form through a heatedreactor at a temperature from 1400 to 1600 F., a contact time of from 2to 10 seconds and a pressure of at least 2.5 atmospheres absolute whilesimultaneously passing hydrogen from an external source through saidreactor at a rate of from 20 to 60 s. c. f. per gallon of saidhydrocarbon, and thereafter separating the fuel gas then formed fromcondensable by-products.

2. A method according to claim 1 comprising, as additional steps,converting a part of said hydrocarbon into hydrogen by initiallyreacting said part with steam to form a mixture of carbon monoxide andhydrogen, thereafter reacting said carbon monoxide with additional steamto form carbon dioxide and additional hydrogen, and thereafterseparating said hydrogen from said carbon dioxide, the separatedhydrogen being fed into said heated reactor as specified in claim 1.

3. A thermal cracking method (in absence of catalyst) of converting ahydrocarbon taken from the group consisting of propane, butane andnatural gasoline into a fuel gas interchangeable with natural gas whichcomprises passing said hydrocarbon in vapor form through a heatedreactor at a temperature of from 1450 to 1550 F., a contact time of from2 to 10 seconds and a pressure of at least 2.5-8 atmospheres absolutewhile simultaneously passing hydrogen from an extended source throughsaid reactor at a rate of from 20 to 60 s. c. f. per gallon of saidhydrocarbon, and thereafter separating the fuel gas then formed fromcondensable byproducts.

4. A method according to claim 3 comprising, as additional steps,converting a part of said hydrocarbon into hydrogen by initiallyreacting said part with steam to form a mixture of carbon monoxide andhydrogen, there- :after reacting said carbon monoxide with additionalsteam to form carbon dioxide and additional hydrogen, and thereafterseparating said hydrogen from said carbon dioxide, the separatedhydrogen being fed into said heated reactor as specified in claim 3.

5. A thermal cracking method (in absence of catalyst) of converting ahydrocarbon taken from the class consisting of propane, butane andnatural gasoline which comprises passing said hydrocarbon through aheated reactor at a temperature of 1400-1600 F., a contact time of 2 to10 seconds and a pressure of at least 2 /2 atmospheres absolute, whilesimultaneously passing hydrogen from an external source through saidreactor at a rate of at least 20 s. c. f. per gallon of hydrocarbon, andthereafter separating the fuel gas then formed from condensableby-products.

References Cited in the file of this patent UNITED STATES PATENTS1,884,269 Russell Oct. 25, 1932 2,072,801 Gary Mar. 2, 1937 2,283,643Nagel May 19, 1942 2,340,815 Lidov Feb. 1, 1944 2,450,753 Guyer Oct. 5,1948 2,605,176 Pearson July 29, 1952 2,608,478 Pollock Aug. 26, 1952FOREIGN PATENTS 531,430 Germany Aug. 10, 1931 481,835 Great Britain Mar.18, 1938

1. A THERMAL CRACKING METHOD (IN ABSENCE OF CATALYST) OF CONVERTING AHYDROCARBON TAKEN FROM THE GROUP CONSISTING OF PROPANE, BUTANE ANDNATURAL GASOLINE INTO A FUEL GAS INTERCHANGEABLE WITH NATURAL GAS WHICHCOMPRISES PASSING SAID HYDROCARBON IN VAPOR FORM THROUGH A HEATEDREACTOR AT A TEMPERTURE FROM 1400* TO 1600* F.8 A CONTACT TIME OF FROM 2TO 10 SECONDS AND A PRESSURE OF AT LEAST 2.5 ATMOSPHERES ABSOLUTE WHILESIMULTANEOUSLY PASSING HYDROGEN FROM AN EXTERNAL SOURCE THROUGH SAIDREACTOR AT A RATE OF FROM 20 TO 60 S. C. F. PER GALLON OF SAIDHYDROCARBON, AND THEREAFTER SEPARATING THE FUEL GAS THEN FORMED FROMCONDENSABLE BY-PRODUCTS.